The Prospectus: If there's any area Maryland is sufficiently well-stocked in right now, it's the defensive line. Basically everyone returns, save David Mackall (who missed the final four games anyway) and Maurice Hampton (who was more or less a reserve), and all three positions are stacked with depth, experience and quality. They give Brian Stewart quite a lot to work with in his first year transitioning to the 3-4.
That transition to the 3-4 will perhaps make things a bit trickier than they would've been otherwise, with Joe Vellano and Andre Monroe moving outside to an end spot and A.J. Francis transitioning to a space-eater role. But they're all fairly well-suited for their new positions, and once they get things down I wouldn't expect any problems.
There is a concern, even just outside the transitioning: even though most everyone returns from last year, Maryland's defensive actually wasn't very good last year. They were maimed by strong rushing attacks, giving up more than 200 yards on the ground seven times (more than 300 twice!) and finishing with the #111 rush defense in the country - only Ole Miss (2-10), Indiana (1-11), Kansas (2-10), and Texas Tech (5-7, by some miracle) were worse as BCS schools. While returning starters is always a good thing, it's a bit less encouraging when they weren't very good to start with.
But I'm optimistic that things will improve. The 3-4 scheme will take some pressure off the line, removing a position and turning it from a potential weakness to what looks like a strength. And the experience factor will help, too: Vellano and Francis are seniors, and now Monroe and Bowers will have seen plenty of action as well. With Isaiah Ross and Justin Anderson hopefully healthy for the entire year, Maryland has more to play with on the defensive line than they ever did last season. With help from an equally experienced linebacker corps, Maryland's front seven - and thereby their rushing defense - should be greatly improved from last season.
Individually, it's easy to look at Vellano and wax poetic (and we will do shortly), but the strength here runs much deeper than just him. A.J. Francis has never been dominant in the middle, but he's been solid and consistent across three years now and is exactly the type of guy I'd want manning the nose spot in a 3-4. It's a good fit given his motor and 300+ size, and will be backed up capably by the equally-big Darius Kilgo and Nate Clarke (who, for what it's worth, I think could make a real impact there in due time).
And there's darn near an embarrassment of riches across Vellano at the other end spot: Andre Monroe is the favorite for the position and adds some penetrative ability to a rather static line, but Anderson has perfect 3-4 size and Bowers was super-productive as a freshman as well. Monroe's one of my favorites on the team this year; he's not a big guy, but stays low, has a killer motor, and is constantly a nuisance in the backfield; he notched five sacks as a true freshman despite missing three games entirely (another three years like that and he'd make a run at Maryland's all-time sacks mark). I expect him to start, with the larger Anderson coming in situationally. But there's really not a weak link here.
Still, it all revolves around Vellano, probably the most productive defensive lineman in the country last year and arguably the best defensive player in the ACC. Everyone knows his story by now: lowly-regarded recruit, greyshirts, redshirts, keeps his head down and works his way into all-America status. He's as active a defensive lineman as there is in the country, with a great head for the game and solid strength and quickness. He's dangerous enough (and well-known enough) to consistently draw a second blocker, which is key in the 3-4 and will open up space for the linebackers behind him. When he does get one-on-one, he'll be able to hold his own against both the run and the pass, and should help take pressure off the others on the line (who may not really need it.) The 3-4 can occasionally stifle defensive linemen, given that their job often is as much to do about attracting blockers as it is about actually making a play themselves; that being the case, I'm not really expecting the same huge numbers he had last season, but I am expecting the same effectiveness. (As a nice bonus, he's backed-up by the very capable Isaiah Ross, who missed most of last season. It'll be a delight to see him back on the field.)
I'd expect plenty of rotation between the various spots; Anderson, Monroe, and Vellano could all move inside situationally, freeing up a more dynamic player like Bowers or Ross to add extra pass-rushing menace. I wouldn't even be surprised to see Ross move back occasionally as a linebacker or Clarence Murphy come forward and put his hand in the dirt. This should be a fluid area in this scheme, and I fully expect it to be. If you're looking to have some fun this year, this could be your best place to do it.
The Future: Things will get trickier next year, when Vellano and Francis have headed out the door, but not desperately so. Isaiah Ross is a ready-made, experienced Vellano replacement, and Nate Clarke and Darius Kilgo isn't a bad nose tackle platoon assuming they get some game time this year. And all of that young depth at the ends - like Andre Monroe, Keith Bowers, and Quinton Jefferson - will have hopefully grown up by the time they're needed to carry the load.
My only real concern is that Maryland doesn't have much in the way of defensive linemen coming in. You don't need too many of them - only three positions, after all - but the only two committed are Malik Jones and Kingsley Opara; Jones is an offensive lineman who'll need time to transition, and Opara's highly raw himself.
Hey, maybe they're going all-in in Da'Shawn Hand. That'd be nice, right?
Optimism: Maryland is very deep here and has plenty of experience across all three spots on the line. Vellano is an elite lineman, Francis is reliable, and the duo of Bowers and Monroe are productive youngsters with room to grow. I have very few worries.
Pessimism: They weren't great last year, and there's always going to be a concern when switching positions. They're all sensible switches (no Tate to linebacker, for instance) but you never know until you see it in the flesh, I suppose.
Random, Baseless Prediction: Vellano makes it through the season unscathed and is exactly what you expect him to be: sometimes quiet in the new scheme, but with a few virtuoso Vellano tackle-everything performances. Some of the other linemen pick up niggling injuries, but Maryland's depth means they're not killers. Monroe finishes the season with seven sacks and is a preseason all-ACC selection going into next year; as a unit, they're a bit stiffer and stronger against the run, though still not stifling.
Final Words: Finally, a position where you don't need to try to talk yourself into Maryland being good. It's quite easy to see that this unit should be good, potentially very good, and is commensurate with or even superior to most of their ACC foes. The impact of a good defensive line is somewhat minimized by the 3-4, but it's still a luxury, and Maryland should be happy they finally have one.